>>27 に書いてある以前の問題だったorz
The upgrade path from 20.04 to 22.04 does not open until after the release of Ubuntu 22.04.1 LTS which is still ~three months into the future. It's the same as prior LTS releases & upgrades

22.04.1を待つか、20.04->20.10->21.04->21.10->22.04を頑張るか、うーん。